Battery Capacity Converter
Convert battery capacity with the factor behind each answer. Charge (mAh, Ah) and energy (Wh, kWh) are different quantities: going from one to the other needs the nominal voltage, so it is a calculation, not a unit change.
1 Ah = 1,000 mAh
Common conversions
- 1 Ah = 1,000 mAh
- 1 mAh = 0.001 Ah
- 1 kAh = 1,000 Ah
- 1 Wh = 0.001 kWh
- 1 kWh = 1,000 Wh
Ah and Wh are not the same thing
Ampere-hours measure the charge a battery can deliver. Watt-hours measure the energy, which is charge multiplied by voltage. A 100 Ah battery holds 1,200 Wh at 12 V and 2,400 Wh at 24 V, so quote the voltage with any Ah rating.
Rated capacity depends on the discharge rate
A battery rating is valid at a stated discharge rate and temperature. Drawing current faster gives less usable capacity, especially for lead-acid, so check the datasheet before sizing a runtime. Usable energy is also limited by depth of discharge.
Nominal voltage
Use the nominal voltage on the datasheet: about 3.6 to 3.7 V for a lithium-ion cell, 3.2 V for LiFePO4 and 2 V for a lead-acid cell. Multiply by the number of cells in series for the pack.
Capacity to energy example
5,000 mAh is 5 Ah. At a nominal 3.7 V that stores 18.5 Wh (0.0185 kWh). The voltage is not part of the unit conversion; it is the second input the energy needs.
Unit factors
Every unit in terms of the base unit shown. To convert, multiply by the factor of the unit you have and divide by the factor of the unit you want.
Battery charge (capacity) units
| Unit | Equals | What it is |
|---|---|---|
| mAh | 0.001 Ah | Milliampere-hour, a thousandth of an ampere-hour. Phone, power bank and small cell ratings. |
| Ah | 1 Ah | Ampere-hour: one ampere for one hour. Lead-acid, lithium and UPS battery ratings. |
| kAh | 1,000 Ah | Kiloampere-hour, a thousand ampere-hours. Large battery banks and electrolysis. |
| C | 0.0002777777778 Ah | Coulomb, the SI unit of charge: one ampere for one second. 1 Ah = 3,600 C. |
| mC | 2.777777778 × 10⁻⁷ Ah | Millicoulomb, a thousandth of a coulomb. |
| kC | 0.2777777778 Ah | Kilocoulomb, a thousand coulombs. 1 kC is about 0.2778 Ah. |
Energy units
| Unit | Equals | What it is |
|---|---|---|
| µJ | 1 × 10⁻⁶ J | Microjoule. |
| mJ | 0.001 J | Millijoule. |
| J | 1 J | Joule, the SI unit of energy: one watt-second. |
| kJ | 1,000 J | Kilojoule. |
| MJ | 1,000,000 J | Megajoule. |
| kcal | 4,186.8 J | Kilocalorie (International Table), 4,186.8 J. Food and thermal energy. |
| BTU | 1,055.055853 J | British thermal unit (International Table). |
| Wh | 3,600 J | Watt-hour: one watt for one hour. |
| kWh | 3,600,000 J | Kilowatt-hour. The billing unit for electricity: one kilowatt for one hour. |
| MWh | 3,600,000,000 J | Megawatt-hour, for utility and plant energy. |
| eV | 1.602176634 × 10⁻¹⁹ J | Electron-volt: the energy of one electron through one volt. |
| keV | 1.602176634 × 10⁻¹⁶ J | Kiloelectron-volt. |
| MeV | 1.602176634 × 10⁻¹³ J | Megaelectron-volt. |
| cal | 4.1868 J | Calorie (International Table), 4.1868 J. The small calorie; a food Calorie is a kilocalorie. |
| GeV | 1.602176634 × 10⁻¹⁰ J | Gigaelectron-volt, a billion electron-volts. Particle accelerator energies. |
Conversion pages
Frequently asked questions
What is the formula to convert Ah to mAh?
mAh = Ah × 1,000. For example, 100 Ah is 100,000 mAh.
How do I convert mAh back to Ah?
Ah = mAh × 0.001. The Swap button above reverses the direction for any pair of units.
How do I convert Ah to Wh?
Multiply the ampere-hours by the nominal voltage: Wh = Ah × V. A 100 Ah battery at 12 V stores 1,200 Wh. The mAh to Wh calculator solves any two of capacity, voltage and energy.
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